function block_four() {

	var block = $("#block_four");
	var w = block.width() - 20;
	var h = block.height() - 15;

	//Original data
	var dataset = {
		nodes: [
			{ name: "Adam" },
			{ name: "Bob" },
			{ name: "Carrie" },
			{ name: "Donovan" },
			{ name: "Edward" },
			{ name: "Felicity" },
			{ name: "George" },
			{ name: "Hannah" },
			{ name: "Iris" },
			{ name: "Jerry" }
		],
		edges: [
			{ source: 0, target: 1 },
			{ source: 0, target: 2 },
			{ source: 0, target: 3 },
			{ source: 0, target: 4 },
			{ source: 1, target: 5 },
			{ source: 2, target: 5 },
			{ source: 2, target: 5 },
			{ source: 3, target: 4 },
			{ source: 5, target: 8 },
			{ source: 5, target: 9 },
			{ source: 6, target: 7 },
			{ source: 7, target: 8 },
			{ source: 8, target: 9 }
		]
	};


	//Initialize a default force layout, using the nodes and edges in dataset
	var force = d3.layout.force()
		.nodes(dataset.nodes)
		.links(dataset.edges)
		.size([w, h])
		.linkDistance([50])
		.charge([-100])
		.start();

	var colors = d3.scale.category10();

	//Create SVG element
	var svg = d3.select("#block_four")
		.append("svg")
		.attr("width", w)
		.attr("height", h);

	//Create edges as lines
	var edges = svg.selectAll("line")
		.data(dataset.edges)
		.enter()
		.append("line")
		.style("stroke", "#ccc")
		.style("stroke-width", 1);

	//Create nodes as circles
	var nodes = svg.selectAll("circle")
		.data(dataset.nodes)
		.enter()
		.append("circle")
		.attr("r", 10)
		.style("fill", function(d, i) {
			return colors(i);
		})
		.call(force.drag);

	//Every time the simulation "ticks", this will be called
	force.on("tick", function() {

		edges.attr("x1", function(d) {
				return d.source.x;
			})
			.attr("y1", function(d) {
				return d.source.y;
			})
			.attr("x2", function(d) {
				return d.target.x;
			})
			.attr("y2", function(d) {
				return d.target.y;
			});

		nodes.attr("cx", function(d) {
				return d.x;
			})
			.attr("cy", function(d) {
				return d.y;
			});

	});

}
block_four();